Why are midge bites so itchy?

Steven Chisholm

The arrival of summer is a welcome occurrence but there’s a flip side for many Brits as the sun finally reappears after a long winter - the return of the dreaded midge.

While there are few that would grudge the return of warmer weather after a seemingly endless winter, many a hiker, dog walker or picnicker has cursed forgetting the insect repellant as swarms of tiny bloodsuckers attack.

Yet some people seem relatively unaffected by the winged beasties.

So why are some people attacked more than others, and why are midge bites so itchy?

There are five species of biting midge in the UK, Culicoides Impunctatus - the Highland Midge - and Culicoides Halophilus being the most notorious. It’s the pregnant female that attacks humans in order to source protein to develop her eggs.

The midge will pierce the skin with her mouth and pump saliva into the wound to prevent it clotting. It’s this saliva which causes a mild immune response in humans, resulting in itchy red spots as the body seeks to repair the wound.

For some, the irritation lasts only a few minutes, but for others the itching can last an infuriatingly long time.

The NHS warns that some can experience bullae - fluid-filled blisters - or weals - circular, fluid-filled areas around the bite - as a result of allergic response to a midge bite.

And, according to some experts, it’s your smell that makes you a midge magnet.

Jonathan Day, a professor of medical entomology at the University of Florida, suggests that biting insects such as mosquitos - and close relations midges - are chiefly attracted by the amount of carbon dioxide you exhale. As well as carbon dioxide, lactic acid and estradiol found in your sweat can act as an attractor.

Your body heat is also thought to be an influence on how attractive you are to midges and pregnant women are thought to be more attractive as a consequence.

So how can you avoid being bitten?

Unfortunately, there’s no foolproof way to avoid midge bites but you could try some of these suggestions:

Long clothing - minimising the amount of skin exposed by wearing long-sleeved T-shirts and avoiding shorts

Smoke them out - some swear by smoke’s midge-repelling qualities. Standing near a BBQ might shield you from harm

Eating Marmite - old wives tale or not, Marmite has long been praised for its ability to put off blood suckers

Insect repellant - seems an obvious one. Most chemical repellants contain di-methyl phthalate (DMP) and di-ethyl toluamide (DEET) as their active ingredient. But read the packaging carefully and seek proper advice if you’re planning on using them on children. According to the Lancet medical journal: “When used sensibly, insect repellents are advantageous and safe, but the potential toxicity of DEET is high and the use of repellents containing more than 50 per cent DEET should be avoided in infants and young children because of their thinner skin. Frequent total body application of DEET for days or weeks should be avoided.”